Strength gains with resistance training are due to muscle hypertrophy and nervous system adaptations. The contribution of either factor may be related to the complexity of the exercise task used during training. The purpose of this investigation was to measure the degree to which muscle hypertrophy contributes to gains in strength during exercises of varying complexity. Nineteen young women resistance trained twice a week for 20 weeks, performing exercises designed to provide whole-body training. The lean mass of the trunk, legs and arms was measured by dual energy x-ray absorptiometry and compared to strength gains (measured as the 1-repetition maximum) in bench press, leg press and arm curl exercises, pre-, mid- (10 weeks) and post-training. No changes were found in a control group of ten women. For the exercise group, increases in bench press, leg press and arm curl strength were significant from pre- to mid-, and from mid- to post-training (P < 0.05). In contrast, increases in the lean mass of the body segments used in these exercises followed a different pattern. Increases in the lean mass of the arms were significant from pre- to mid-training, while increases in the lean mass of the trunk and legs were delayed and significant from mid- to post-training only (P < 0.05). It is concluded that a more prolonged neural adaptation related to the more complex bench and leg press movements may have delayed hypertrophy in the trunk and legs. With the simpler arm curl exercise, early gains in strength were accompanied by muscle hypertrophy and, presumably, a faster neural adaptation.

Presumably this was due to requiring a longer time to learn (i.e. get past the neural adaptation phase). Well I found it. In that article, I talked about how one factor in the neural adaptations has to do with coordination, basically learning how to perform the exercise. What I didn’t really get into since I ran out of time and space is the time course for neural versus growth. Or why I think it might work that way.

First let me throw out a bit of wanky speculation on the topic. At a base level, the human body is pretty efficient. Efficient in the sense that it tries to minimize it’s energy expenditure as a survival strategy. And at a fundamental level neural adaptations to training don’t cost anything outside of practice time. It doesn’t take any real energy for the nervous system to adapt but the body gets better at the movement and grows stronger.

In contrast, growing muscle is highly energetically expensive, to build one pound of muscle takes about 2700 calories or so (it also takes some calories to maintain). That’s energy that could be used for other things. So the body might prefer to make neural gains first. Yes, this is speculation. No, I’ve never seen any research on this or even anybody but me hypothesizing this although someone might have. It could be wrong and I’m ok with that. It kind of doesn’t matter in the big scheme.

Arguably a bigger issue is this: anybody who has taught or learned a complex movement knows, part of this is that you can’t really work the muscles involved hard until you can do the movement safely. It takes weeks to get competent enough at say, a squat, to be able to really challenge the muscles. The same goes for almost any complex movement that can be done in the weight room. Yes, you may be able to learn basic technique quickly but competency and the ability to use heavy weights takes time.

I mentioned in one series or another that the Olympic lifts kind of suck for muscle growth. One reason is just the nature of the lifts and how they are done. But the main one in the context of this paper is that they take a while to get good enough at to perform with challenging weights. I’d say the same in terms of using them to get stronger (and their primary goal is really power anyhow): it takes so long to get good at them that you’re better off with something less complex.

I’d say the same thing about swimming for fitness and health or even fat loss. People suck at swimming and it takes a long time to get technically competent enough to burn a lot of calories doing it or even do it well. My speed skating coach used to comment that it would be a couple of years before he could really “train” us on the ice for the same reason. Until your technique is good, you can’t really get much done. So we developed most of our fitness with donkey work on the bike and in the weight room until we could skate well enough to really train effectively.

Now contrast that to simpler activities. I can put someone say a leg extension machine and hammer their quads. There is no technique. I can teach someone a biceps curl in about 1′ and work them hard. I can’t do that in a powerclean or something more complex. Yes, there may still be some neural adaptations but in the aggregate there is no real learning that has to happen: I could take someone to failure on day 1 and I can’t do that in a squat. Everyone knows how to walk and even riding a bike is technically not complex (the same goes for the EFX or stepper). Compared to swimming I can work someone much harder on either from day 1. I wouldn’t but I could.

But the take home from this is that, the quicker someone can get through the neural adaptation/coordination phase, the sooner they can start building muscle mass. And the more complex an exercise, the longer getting through that adaptation/coordination/learning phase will take. And that brings me to today’s paper.

The Paper

The paper recruited twenty nine females with no weight training experience. Yes, they were beginners but that’s the point of this since neural adaptations are primary in beginners. A combination of exercises was performed including bench press and leg press (defined as the complex movements), arm curls (defined as a simple movement) along with lat pulldown and triceps extension for upper body and leg extension and leg curl for lower body.

Upper body was worked for 5 sets of 6-10 repetition maximum (6-10RM, the most weight that can be lifted 6-10 times) and lower body for 5 sets of 10-12RM (based on earlier observations that most can do more reps with legs). The training program lasted 20 weeks (generally far beyond when most work shows the neural adaptations to predominate).

Ten of the subjects performed all exercises on the same day while the other group did an upper/lower split four days per week (this was analyzed in a separate study). Workouts and exercises were supervised. The primary focus of the study was on the leg press/bench press (again, complex) and arm curl with measurements of arm, leg and trunk muscle mass changes made by DEXA. Trunk here was to measure the impact of bench press so think of it as the chestal/back area.

Measurements were made pre-training, at the midpoint (10 weeks) and post-training. And what they wanted to see was if there were differences in the time courses for muscle growth in those different areas since they were being worked by relatively more or less complex movements. 1RM strength was also measured.

Results

1RM strength in all movements improved and to about the same degree although they started to taper off by about week 10 (presumably the major neural adaptations had been accomplished) and I’m not providing the data since it’s not really my focus. Rather, let’s look at the changes in muscle size as there was a difference.

In the arms (worked by arm curls the simple exercise) the major gains in muscle size occurred in the first 10 weeks and then slowed down while in the trunk and legs (worked by the more complex bench and leg press), the major gains took place between week 10 and 20.

Click me to embiggen

In the arms, at 10 weeks there was a statistically significant increase in size from the start of the study, what appears to be slight increase at week 20 wasn’t statistically significant. In the trunk, I think it’s more visible since there was basically no growth from start to mid point and then some growth by week 20. Finally in legs, the small visual increase in size wasn’t statistically significant at week 10 but was by week 20.

Discussion

As all good researchers do, a number of limitations were brought up in the discussion. One had to do with the fact that more than just three exercises (leg press, bench and arm curl) were done. They state

One limitation to the present study was the use of other exercises that trained the same musculature as the bench press, leg press and arm curl. These additional exercises were used in a study of the effects of whole- versus split-body weight training routines

A more controlled study might look at just those three movements. Or compare just squat or leg press to curl and see what happens (and given that squat is more complex to learn than leg press I think the difference might have been even greater). That is, just compare one complex and one simple movement. Because it’s possible that growth in say, the arms was as much due to the bench and pulldown as the simple movements. Mind you, the legs also had two simple movements and they still took longer to grow.

A question that might come up is if this applies to men as well as women, another question the researchers used. Perhaps due to different levels of early training there would be a gender difference. OR men might make different gains due to differences in overall growth potential. But most studies find that women and men, beginners at least, make the same relative gains in strength and size in response to training. Women’s absolute increase is smaller (because 10% of 100 is less than 10% of 150) but the relative increase is the same.

I’d mention that, even due to activities of daily living, the lower body usually gets some work (walking, climbing stairs) while the upper body frequently does not. It’s possible that some of the difference in growth is related to this. We know that untrained muscles grow more effectively than trained muscles so perhaps the relatively less trained nature of the upper body is responsible for the faster growth. Since this study and the one linked above did have some simple leg movements that didn’t cause growth, I see this as a possibility.

Regardless, the researchers conclude:

In summary, our results indicate that training with complex exercises (bench and leg press) causes delayed muscle hypertrophy when compared to a less complex exercise (arm curl). This may be due to a prolonged neural adaptation when training with complex exercises.

My Comments

Ok, so that’s the paper, results and discussion. Let me finish with my comments. If I really wanted to kick off a shitstorm in the comments, I’d simply conclude from this that complex exercises, at least for beginners, are arguably inferior for muscle growth. The studies support that. Which isn’t to say that more complex movements can’t or shouldn’t be done from earlier on if desired; it’s simply that if increasing muscle size/improving body composition perhaps they aren’t ideal in the initial stages of training since the neural adaptations will take longer to “complete” (for lack of a better word).

Another aspect of complex versus simple movements is that often more complex movements are limited by stabilization issues. The rotator cuff in the bench, various stabilizers in other movements have to reach a point where they aren’t limiting the movement.

I know that people have a huge hardon for the stabilization and more complex movements being superior for growth but, fundamentally, if the goal is to train the prime movers, you want LESS stabilization requirements rather than MORE since the higher the stabilization component, the less force can be generated and the less that the primary movements in the exercise can be trained.

But while we will all agree that the Swiss ball is shit for growth since you spend most of the time stabilizing, somehow if you go past the flat bench (everybody’s favorite exercise) and suggest an even more stable movement (i.e. a Hammer machine), suddenly you don’t know how to train despite the clear fact that the lack of stabilization requirements lets you hit the PECS more effectively (which is the goal for GROWTH is it not).

Basically there is this weird line drawn in the sand where too far to one side is too unstable but too far to the other is too simple/no es mas macho, etc. But that just represents hardhead myopia for ‘basic barbell training, grunt grunt’ and I’m off topic. Sure, if you gotta get stronger in bench, you have to bench. If you want to improve your squat, you have to squat. But if you just want big legs…

But if the goal is only muscle size, at least in the short-term for beginners it would appear that simpler movements are more effective. Which is not to say that a mixture of complex and simpler movements shouldn’t be done. But if the goal is size, including some simpler movements (i.e. get away from the asinine bench, squat, DL only type of training) makes sense. If the goal is NOT size for some reason, perhaps deliberately choose to avoid simpler movements.

And I could even wank that the choice might then have a gender basis. Men usually want to get jacked (and strong) and the faster they can get/see/feel measurable growth the better. They also LOVE training the arms. So give them some direct bimer and trimer work (look up Body by Jake to get this).

In contrast women frequently fear gaining muscle size and deliberately focusing on more complex movements might be superior in this sense. My experience is that once women start to feel stronger (without necessarily getting bigger) they often get much more interested in strength training.

It’s empowering (insert riot grrllll stuff here) and when they notice that their life is easier (or as in the case of one of my clients, she could kick her husband’s ass when they wrestled) it becomes a feed-forward cycle where they want to start pushing more. By the time the increases in muscle size (which are always small in any case) start to show up, they are usually hooked.

Conclusion

But that’s that. In the short-term for beginner, more complex movements, within the limitations of this (and other studies) appear to give POORER muscle growth while strength is being gained with the growth from simpler movements showing up earlier. I’m not saying to not start with a mixture as appropriate, it’s just important to realize that, depending on goal, a relative focus on one or the other may be more important in the early stages of training.

And now I shall wait for the first person in the comments to claim that I only recommend simple/ isolation movements for or have this article claimed to say that elsewhere on the Internet. Because that’s just how it goes….